Vehicle doors having a structure such that door frame (sash) is mounted onto a door panel are provided, in addition to side sashes that project from the door panel to form a window opening, with lower sashes that guide a window class in the door panel. Conventionally, the lower sashes have been positioned and fixed independently with respect to the door panel (an inner panel which constitutes a part of the door panel), separately from the side sashes. For instance, in the vehicle door sash disclosed in Patent Literature 1, an approximate position of each lower sash can be set by inserting a lug provided at the upper end of the lower sash into the associated side sash (upper sash). However, in order to tolerate variations in part accuracy and assembling accuracy, a clearance is provided between each lower sash and the associated side sash (upper sash) in the sash lengthwise direction, so that a delicate position adjustment needs to be made to each lower sash in the sash lengthwise direction when the lower sashes are fixed to the door panel.